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NAPHTHALENE

TABLE   XL
Character and Composition of Benzoles


	
	
	Composition.
			
Mark and Denomination.
	Specific Gravity at 15° C.
	Percentage of Distillate at different temperatures.
	
			
			Ben-
	Tolu-
	Xyl-
	Higher


	
	
	zole.
	ole.
	oles.
	


	
	
	
	
	
	logues.

I (90% benzole)   .
	0-880-0-883
	90-93% up to 100°
	84
	13
	3
	

II (50% benzole) .
	0-875-0 -877J
	5°-53% up to 100° 9°-93% UP to I20°
	43
	46
	ii
	—

Ill       .....
	0-870-0-872
	90% at 100-120°
	15
	75
	10
	—

IV ......
	0-872—0-876
	QO% at i^o— id.T°
	
	2S
	70
	_

V (solvent naphtha) .
	0-874-0-880
	90% at 130-160°
	—
	5
	70
	25

VI      ,,
	0-890-0-910
	90% at 145-175°
	—
	—
	35
	65

Heavy benzole    .
	0-920-0-945
	90% at 160-190°
	_
	1       -
	5
	95

These benzoles contain varying proportions of impurities. Thus, thiophene
is always present in the earlier of the above marks and carbon disulphide occurs
to the extent of 0-2-1 % in benzole I and 0-0-5% m benzole II, whilst it is usually
absent from succeeding marks. In marks I, II and III, the amount of paraffin
hydrocarbons is at most i%, and in other marks rather more. Pure benzoles
are coloured by o-i c.c. of the bromide-bromate solution, but the commercial
products require 0-6-1%.

As regards the behaviour of the principal commercial products on fractional
distillation with a rectifier for the separation of the individual hydrocarbons
(see above, 3), the following serve as examples :

First fraction

Benzole

Intermediate fraction .

Toluole

Xyloles

Higher homologues, etc.

The proportions   of the three  isomerides in commercial xylole are about
76-5 of m-, 15 of p- and 5 of o-xylene.


	
	Pure com-
	Com-           Com-
	
Benzole
	Benzole
	mercial
	mercial       mercial
	
I.
	II.
	Benzole.
	Toluole.       Xylole.
	
1-0%
	o-3%
	o-5% )
	
	

78-8%
	18-3%
	98-0%   \
	o-3%
	JOO/

10-0%
	47-5% ^
	J
	
	

8-0%
	237%
	
	97-3% .
	

}   2-2%    j
	10-2% j
	
	2-A°/          96'5%
 24/0         2.2o/Q
	
NAPHTHALENE

This is marketed in different degrees of purity : crude, coloured brown
by tar oils and other impurities, and moderately pure, in more or less large,
white or faintly yellow, lamellar crystals. The tests usually made to
determine the purity are as follows :

1. Melting and Solidification Points.—These are determined by
means of Shukoffs apparatus (see Chapter on Mineral Oils, Solid Paraffin,
2), the inner test-tube being half filled with the fused naphthalene and a
thermometer reading to 0-1° immersed in it. On immersion the ther-
mometer bulb becomes covered with a layer of solidified naphthalene; it are shaken for 15 minutes in a separating